Rotary percussive power tool



Aug. 2, 19.60 J, QROS ROTARY PERCUSSIVE POWER TOOL Filed Nov. 4, 1958JNVENTOR. JOHN OROS ATTORNEY Unite This invention pertains to the art ofrotary percussive power tools, and more particularly to a device forapplying an axial percussive force to the working end of a rotating,cutting tool.

The invention'is particularly applicable to a device adapted to bemounted between a portable electric drill and a rotatingtungsten-carbide tipped drill, and will be described with particularreference thereto although it will be appreciated that the invention hasbroader applications, and for example, may be incorporated in theportable electric drill itself, or in fixed apparatus if desired.

In the art of drilling cement, masonry, or other nonmetallic substances,it is known that substantially increased drilling speeds and more rapidcutting can be obtained if, while the drill is being rotated in contactwith the work, an axial percussive force is periodically applied to thedrill. Such percussive force drives'the cutting edges of the drillaxially into the cement, or the like, to greatly accelerate the drillingoperation.

Various means have been proposed in the past to obtain this result, forexample, a cam rotating with the drill and having a gradual axial rise,and an abrupt dropoif, together with a spring biased follower which ispushed back by the cam and allowed to drop'abruptly to impart ahammering action on the cam and thus on the drill. However, thehammering action-on the cam surfaces caused excessive wear on thesesurfaces with the result that the manufacture of a long-lifetoolwasextremely difiicult and expensive. a v

Furthermore, it has been impossible with previous States Patent2,947,180 ,Patnted Aug. 2, 1960,

member is spaced from the cam surface of the cam member at the point ofabrupt drop-off when the hammer surface engages the anvil surface of thetool holder.

Further in accordance with the invention, means are provided to adjustthe cam member toward and away from the follower, to vary the length ofstroke of the hammer member and consequently the percussive forceapplied to the working end of the tool; The cam member is adjustablebetween a first position in which the cam and follower surfaces justclear each other at the point of drop-off when the hammer and anvilsurfaces are engaged, and a second position in which the cam and 01-lower are maintained out of engagement during rotation of hammer member.

Further in accordance with the invention, the tool holder is mounted ona drive shaft'of a rotary drill and is capable of a small degree ofaxial movement relative to the shaft so that transmission of percussiveeffects to portions of the device other than the tool holder an tool isminimized or eliminated.

The principal object of the invention is the provision of a new andimproved device for applying a percussive. action to a rotating drillwhich has improved operation, is simple to use, and enables thepercussivev actiontogbe readily controlled- Another object of theinvention is the provision'of a new and improved device of a generaltype'described wherein the hammer or percussive action takes place onsurfaces other than the cam and follower surfaces.

Still another object of the invention is the provision of a means forvarying the percussive force applied to the tool. Z

A further object of theinvention is the provision in such a device of ameans for selectively discontinuing the percussive effects. 4

A still further object of the invention is to mount the tool holder ofthe ,device in a manner such thattransmission offthe percussive effectsto parts of said device other than the tool holder and tool is minimizedor eliminated.

The invention may take physical form in certain parts and arrangementsof parts, a preferred embodiment of knowndevices to vary the amount ofpercussivetorce applied to the tooljor to eliminate the percussionentirely; The inabilityto achieve'this often resulted in break, age ofthe brittle drill tips when initially starting into work, because of thehuge force exerted over a small area of-the drill tip. 1 a

The "present invention contemplates a new and improved device forapplying a percussive action to a' rotatingildrill which overcomes theabove-mentioned difficultiesofth prior art, and others, and provides ado:

viceywhich is simple in construction, rugged in 'dp'eration, easytom'anipulate, and which is economical to construct.

ing acam follower surface separate from the hammer surface.v .Thecamfollower surface of the hammer mern-f her is adapted to--rotate andcooperates with a stationary cam member having anaxial rise and anabrupt drop-01f.

Spring means biases the hammer member toward the fanvil surfacesandsupplies the hammering force when theflcam, follower surface reaches thepoint of abrupt ,dropofiof-the cam.

j .Eur'ther in accordancewith the invention, the parts are so. arranged,that the cam following surface of the hammer which will be described indetail in this specification, and illustrated in the accompanyingdrawings which form a part hereof, and wherein: I V l Figure 1 is asidecross-sectional viewwith portions partly in elevation of a devicefor applying a percussive action to a rotating drill illustrating apreferred embodia ment of the invention; Figure 2 is a cross-sectionalviewof Figure 1 taken approximately on the line 22. thereof; Figure 3isa cross-sectional view of Figure 1 taken approximately on the line3-3thereof; and, 1 Figure 4 is a cross-sectional view of 'Figure 1 takeapproximately on the line 4-- 4 thereof. r

Referring now to the drawings wherein the showings are for the purposesof illustrating a preferred embodiment of the invention only, and notfor the purposes of limiting the same, the figuresshow a device forapplying a percussive action or effect to a rotating drill comprised ofa drive shaft 1i) rotatable in a fixed member in the form of a housing11 and rotatably driven on the righthand end by suitable power means(not shown), A tool holder 12 is'slidable on, and keyed to the oppositeor left-hand end of the shaft 10. This tool holder 12'extends beyond theleft-hand end ofthe housing ll and has an opening to receive the shankend of a drill 13 which drill is held in the holder 12 by any suitablehold ing means such as the set screw 14. h V Q Means are provided forapplying end thrust from the shaft 10 to thetool holder 12 and for atleast partially 3. absorbing thrust from the tool holder to the shaft inthe same direction. Such means may be of any suitable type, but as shownherein comprise a thrust collar mountednear the left end of the shaftlflandseated against the,bott om of a counterbore in theright end of;the,tool holden As illustrated, the thrust collar, consists, of. a pairof c shaped pieces which fit into agroove. near theendof the shaft. Aretainingnut 16 is threaded onto-,th'e extreme left-hand end of theshaft 10 to secure thetoolholderlz to the shaft 10. In order to permita, small degree of axial movement of the tool holder relative to theshaft, the threaded endof the shaft. is

shouldered so that the distance between thethrust collar,

and the retaining nut, when locked imposition, is slightly greater thanthe distance between opposed shouldersin the tool holder cooperatingwith the thrust collar and nut 16.

An anvil surface 17 is provided at the right-hand end of, the toolholder 12 to receive periodic, blows from a hammer surface 18 on theleft-hand of a hammer member ,1 9. Any suitable means may be provided topcriodically reciprocate the hammer member :19 to cause the hammersurface 18 to strike the anvil surface 17 of thetool holder and drivethe drill 13 into the work. Inthe preferred embodiment shown, the hammermember has a follower surface 20 adapted to cooperate with a cam,surface21 on a stationary cam member 22 fixed against rotation relative to thehousingll, 'Ihehammer member 19 is keyed to andaxiallyslidable'on theshaft 10 and rotates relative to the cam member 22. The surface 21 ofthe cam member is formed as an axial rise followed by an abrupt drop-01f23. There are two such cooperating surfaces and drop-offs shown on eachthecam member 22 and hammer member 19. Accordingly, as the hammer member19 is rotated with the drive shaft 10, it is driven each time to theright to lift the hammer surface 18 from the anvilsurface 17.-for eachhalf revolution of the shaft. A helical compressionspring 24 biases thehammer member 19 in'the direction toward the tool. holder 12 and isadapted, when the point of abrupt drop-01f immediately following thehigh point of the cam surface 21 is reached, to impart a sudden leftwardmovement to the hammer member to effect a percussive blow against theanvil surface '17 of the tool holder 12. The spring 24 seats between awasher, 25 and the bottom of a counterboreinthehammer member 19.

Means are provided to adjustably move the cam member 22 axially relativeto the hammer member 19 so that the effective portion of the camsurface21 engaged by the follower surface 20 may be varied to limit thelength of stroke of the hammer member. As shown, the cam member 22 iskeyed-to the housing 11 with an elongated keyway being provided in thehousing to en ableaxial movement of the cam member. Adjustment of thecam member 22 is accomplished in a rightward direction by rotation of anormally fixed second cam member 26 and in the leftward directionby apair of springs 27 urging the cam member 22 against the member 26, andthe latter against a seat in the housing 11. Theopposite end of thesprings 27 seat between the housing 11 and cam member 22. The second cammember 26' has an axially inclined surface 28 mating witha correspondingsurface-29 on the cammember 22., The member 26 is capable of 180rotation-relative to the housing 11, to move thelcamymember 22from aleftwardposition shown in Figure l. in which the surfaces 20 and 21 aremaintained out of engagement during rotation of-the hammer member 19, toa second rightwardposition in which these surfaces are closely spacedbut separated when the hammer and anvil surfaces 18 and 17 are inengagement. The cam member 22 may be infinitely adjusted between; thesetwo; positions to: enable selection by; the operator-cf the..extent 10fpercussive force below the surface.

applied to the anvil surface of the tool holder, by varying the lengthof stroke of the hammer member. In any position of adjustment, therewill preferably always be a clearance between the follower surface 20and cam surface 21 at the point of abrupt drop-off when the hammersurface 18 strikes the anvil surface 17. The entire force of the springwill therefore be absorbed between the surfaces 17 and' 18 and notbetween the surfaces 20 v 4 131 21.

It isobvions that means other than the second. cam member 26 may beprovided to shift the cam' member 22 axially. The-cam member 26 wasselected for this purpose because it can be easily manufactured from thesame stock as the cam member 22. They are made from a sleeve whichserves not only the functions aforementioned, but also journals the toolholder 12, hammer member 19, and thereby, the left end of the shaft 10.

Any means may be provided to rotate the second cam member 26. Preferablythis means is in the form of a sleeve 30 rotatable-on the exterior ofthe housing 11 between a shoulder in the housing and a retaining nut 31.A set screw 32 is threaded radially into the member 26 with itsv headextending outwardly through the sleeve 30. A circumferential slot 33 isprovided about of the housing 11 and also receives the head of the screw32. The ends of the slot serve as limits of rotation for the second cammember 26.

The adjustable stroke. of the hammer member is provided for thefollowing purpose. The tips of tungsten carbide drills are easily brokenwhen great impact is provided over a relatively small area of the tip.Because. of this, the percussive action is disadvantageous when firststarting to drill into a surface. Consequently, it has been necessaryinthe past to compensate for the difference between the highestpermissible starting force limited by the point at which a drill wouldbreak, and the much higher force desirable once the drill tip wascompletely below the surface of the work. This was done by selecting aspring having a force which was sufficiently low to prevent breaking ofthe drill tip when starting to drill, but which was also sulficientlyhigh to give a fairly effective percussive action once drilling wasunder way. I have found that'by eliminating the percussive blowsinitially and then increasing the force steadily to a much higher force,I'not only prevent breaking of the drill tip, but am able to get muchhigherpercussion than previously,- oncethe drill tip is into and Theforce of the spring 24 need no longer be limited, by the breakage pointofthe drill tip when starting. It is now limited only by the maximumpermissible percussive force at whicha; drill tip will break'when thefull area of the cutting edge .isin contact with the subject beingdrilled. Therefore, I can get much higher impact force applied tothedrill tip, and consequently much more rapid andefiicient drilling.

In the preferred manner. of operation of the device,

when, the operator is ready to commence drilling, he will grasp thesleeve and rotateit to thatend of its travel in the slot whichcausesmovement of the cam member to itsposition shown in Figure 1 toprevent reciprocation ,andthereby adjust the cam member 22 towardthefollower surface 20. This will steadily increase the length ofstrokeand the percussive force of the hammer member 19. Oncethe'tip of theme!is fully into the work, he may rotate-the sleeve =30 to the other limitpermitted by the slot--33 to increase the length-of stroke to-itsmaximum.- During the entire operation, the full impact of the hammermember 19 will be absorbed by the anvil surface 17 of the tool holder 12upon being struck. by the hammer surface 18, since the surfaces 20 and21 cannot engage when the spring ,241rapidly' moves the hammer member 19leftwardly-at the point of abrupt drop-off.

. It will furtherabe appreciated that in normal operation of'the device,the drill will be forced into the work by "the operator. Therefore, thedrive shaft will have a by the-pieces will engage its correspondingshoulder a in the tool holder 12 with a small amount of clearanceexisting between the nut 16 and its corresponding shoul-' der in thetool holder. Now, after the cam member 22 has lifted the hammer memberbeyond the point of abrupt drop-off and the spring has caused the hammersurface 18 to strike the anvil-surface 17, the impact will move the toolholder leftwardly relative to the shaft, causing a. slight momentaryseparation between the thrust collar and its cooperating shoulder in thetool holder. The

movement is permittedby the clearance between the nut 16 and itscooperating shoulder. The percussive blow is thereby imparted primarilyor solely to the tool holder 12 and drill 13. Transmission of the blowto other parts of the device will be minimized or possibly eliminated.While the hammer member 19 continues to rotate with the drill and againstart its rightward movement, the hammer and anvil surfaces will againbe separated and the force of the operator in bearing down on the drillwill again cause the thrust collar to engage the shoulder in the toolholder.

The invention has been described with reference to a preferredembodiment. It will be appreciated that modifications and alterationswill occur to others upon a reading and understanding of thisspecification, which modifications and alterations will differ radicallyinappearance from the preferred embodiment. herein described. It is myintention to include all such modifications and alterations insofar asthey come within the scope of the with, said hammer member having ahammersurface cooperating with the anvil surface of the tool holder, andmeans for imparting an intermittent reciprocation to said hammer member,said last-named means including a fixed cam having an axial rise and anabrupt dropoif, a follower on said hammer member and cooperating withsaid cam, spring means biasing said follower toward said cam and saidhammer surface toward and into pressure engagement with the anvilsurface, said cam and follower members having a clearance at thepoint ofabrupt drop-off when the hammer and anvil surfaces are in engagement.

2. A device for applying axial percussive effects to a rotating toolcomprising in combination a member fixed against rotation, a drive shaftrotatable and axially immovable relative to said fixed member, a toolholder rotatable with said shaft and receiving said tool, said holderhaving an anvil surface facing in the direction opposite to the workingend of said tool, a hammer member axially slidable relative to saidshaft and rotatable therewith,

axially toward or away from the follower toincrease or decrease theeffective portion of the axial rise of the cam engaged by the follower,to thereby vary the length of stroke of said hammer member andconsequently the percussive force applied'to the tool. 7

3. A device according to claim 2 in which the adjusting means isoperable to move said cam between a first position in which the cam andfollower just clear each other at the point of abrupt drop-off when thehammer and anvil surfaces are engaged, and a second position in whichthe cam and follower are maintained out of engagement during rotation ofthe hammer member.

4. A device for applying axial percussive elfects to a rotating toolcomprising in combination a housing fixed against rotation, a rotatabledrive shaft extending into said housing from one end thereof and beingaxially im movable relative thereto, a tool holder slidable on androtatable with said shaft, said tool holder having a tool receivingportion facing outwardlyof the other end of the housing and an anvilsurface facing inwardly of the. housing, .a reciprocable hammer memberaxially slidable on said shaft and rotatable therewith, said hammermember having a hammer surface cooperating with the anvil surface of thetool holder, a cam member coaxial with said shaft and having an axialrise and an abrupt dropoif, said hammer member having a follower portionindependent of said hammer surface which follower portion cooperateswith said cam member to intermittently drive the hammer member in adirection away from the tool holder during rotation of the .drive shaft,and spring means biasing said hammer member in the direction toward saidtool whereby a power stroke is imparted to the anvil. surface of thetool holder by the hammer surface of the hammer member each time thefollower portion of the latter drops off the rise of the cam, and saidcam member and follower portion of the hammer member have a clearance atthe point of abrupt drop-01f when the hammer and anvil surfaces are inengagement.

5. A device for applying axial percussive effects to a rotating toolcomprising in combination: a housing fixed against rotation, a rotatabledrive shaft extending into said housing from one end thereof and beingaxially im movable relative thereto, a tool holder slidable on androtatable with said shaft, said tool holder having a tool receivingportion facing outwardly of the other end of the housing and an anvilsurface facing inwardly of the housing, a reciprocable hammer memberaxially slidable on said shaft and rotatable therewith, said hammermember having a hammer surface cooperating with the anvil surface of thetool holder, a cam member coaxial with said shaft and having an axialrise and an abrupt drop-olf, said hammer member having a followerportion independent of said hammer surface which follower portioncooperates with said cam member to intermittently drive the hammermember in a direction away from the tool holder during rotation of thedrive shaft, and spring means biasing said hammer member in V thedirection toward said tool whereby a power stroke said hammer memberhaving a hammer surface cooperat- I with the anvil surface, and meansfor adjusting the cam is imparted to the anvil surface of the-toolholder by the hammer surface of the hammer member each time the followerportion of the latter drops ofi the rise of the cam, and said toolholder is mounted on the shaft between opposed shoulders thereof and iscapable of slight axial movement relative thereto.

6. A device for applying axial percussive effects to a rotating toolcomprising in combination: a housing fixed against rotation, a rotatabledrive shaft extending into said housing from one end thereof and beingaxially immovable relative thereto, a tool holder slidable on androtatable with said shaft, said tool holder having a tool receivingportion facing outwardly of the other end of the housing and an anvilsurface facing inwardly of the housing, a reciprocable hammer memberaxially slidable on said shaft and rotatable therewith, said hammermember having a hammer surface cooperating with the anvil surface of thetool holder, a; cammember" coaxial wtih said shaftand'having anaxialrise; and an abruptdropoff, said -harnme r member having a followerportion in dependent of said hammer surface which'follower portioncooperates with said cam member to intermittently'd-rive thehammer'member in-la direction away from the; tool holder during rotationof the drive shaft, and'springmeans biasing'said hammer'member in thedirection toward said toolholder by the hammer surface of the hammer;member each time, the follower portion of the-latter drops off the riseof the cam, and means for adjusting the cam member axially to increaseor decrease the effective portion of the axial rise of 'thecam' engagedby the follower to thereby vary the length of stroke of said hammermember and consequently the percussive force applied to the, tool.,

7. A device according to claim 6 in which the adjusting means areoperable to move said cam betweenafirst position in-which thercam andfollower just clear each other atthe point of abrupt drop-off'when thehammer and anvil surfaces are engaged, andasecond position in which thecam and follower are maintained'out of 'engagement during rotation ofthe hammer member.

8 A device according to claim 6 in which said housing is' tubular, andin which said: adjusting'means comprises a rotatable sleeve mounted onsaid housing'and operatively connected to said cam member. d

9. A device according to claim 8 in'which said cam member is providedwith an inclined'surface on its end remote from the follower, and inwhich a second cam member fixed" tosaid sleeve is rotatable therewithand cooperates with the inclined surface to eifectuate the adjustment ofthe first cam member. 7

10. A device according to claim 9 in which spring means intermediatesaid housing and the first cam member urges said cam members in adirection away from the follower portion of the hammer member.

11; A device for applying axial percussive effects to a rotating toolcomprising in combination a member fixed against rotation, a drive shaftrotatable in and axially immovable relative to said fixed member, a toolholder rotatable with said shaft and receiving said tool, said holderhavingan anvil surface facing inthedirection opposite to" theworking'end of-tbetool, a'reciprocable hammer member having a hammersurface engageable at OD'blfld of its reciprocating stroke with saidanvil surface to impart a blow to said .anviI surface and there by tosaid to'ol, means for reciprocating said hammer member, and manuallyoperable means cooperatively associatedwith said reciprocating means forvarying'the length of stroke of the hammer-member, said reciprocatingmeans comprising'a cam member fixed' against rotation relative to thefixed member, said cam member having an axial rise and anabrupt'drop-oif, a follower on said' hammer member androtatable withsaid shaft; and spring'means urging'the hammer surface toward said anvilsurface.

12. A device for applying axial percussive effects to a rotating toolcomprising in combination amember fixed against rotation, a drive shaftrotatable in and axially immovable relative'to said'fixed member, meansfor rotating said shaft, a tool holder rotatable with said shaft andreceivingsaid tool, said'holder having an anvil surface'facing in thedirection opposite to the workingend ofthe tool, a reciprocable hammermember having a .hammer surface engageable at one end of its stroke withsaid anvil surface and rotatable-with said shaft, means forreciprocating said hammer member asit rotates;

manually operable means for disabling said reciprocating means, saidhammer member reciprocating means comprising cooperating cam andfollower members, and said disabling means comprising means foradjusting the position of said cam member to alter the effective portionof the cam engaged by the follower, whereby the length of stroke, of thehammer member and consequently the percussive force applied to theworking end of the tool maybe varied.

References Cited in the file of this patent UNITED STATES PATENTS1,665,173 Misener Apr. 3, 1928 2,457,565 Kott Dec. 28, 1948 2,630,723Gridley Mar. 10, 1953 2,794,621 Beeson June 4, 1957

